Atmospheric composition of the warm Neptune HD 106315 c observed by JWST

Star system: HD 106315 | Distance from the Sun: 356 light years

The atmospheric makeup of the warm Neptune-sized planet HD 106315 c has been studied using data from the James Webb Space Telescope. Located around an F-type star, the planet is subject to intense ultraviolet radiation. While researchers expected to find chemical markers related to sulphur, the study revealed a high enrichment of metals in the planet's atmosphere and identified water vapor along with potential traces of ammonia.

By analyzing light passing through the atmosphere of HD 106315 c using the Mid-Infrared Instrument on the telescope, the composition was mapped between 5 and 12 micrometers. This was combined with previous data from the Hubble Space Telescope and new monitoring of the host star's X-ray and ultraviolet activity.

The findings confirm the presence of water in the atmosphere of HD 106315 c, pointing to a metal-rich environment. No clear signs of sulphur-based molecules were detected despite the strong stellar radiation, suggesting the planet may exist in a chemical regime that limits their presence or that the planet has a specific carbon-to-oxygen ratio.

Key findings
- Water vapor was detected in the atmosphere of HD 106315 c.
- Tentative evidence indicates the presence of ammonia.
- Stringent limits were placed on the presence of methane, sulphur dioxide, and carbon disulfide.
- The planet exhibits a strongly metal-enriched atmosphere.
- The absence of sulphur-bearing molecules suggests the planet sits near a transition point between chemical regimes.

Scientific study

JWST-SUPER I: New insights into irradiated warm Neptunes atmospheres from MIRI observations of HD 106315 c (external link)